Pressure relief valves of this type are used to allow gases to escape from the interior of a flexible container as gas pressure builds, or is emitted from the packaged substance, without allowing the packaged material to leak out of the container, nor outside gas or moisture to enter the container in the process. Existing designs for pressure relief valves of this type are many and varied, but conform to the basic structure of a valve body shaped to provide a valve chamber with a valve floor or seat that provides an opening or openings into the container, combined with a resilient diaphragm resting within the valve chamber that acts as a flap or plug covering the opening or openings. As gases build up and escape, the diaphragm is lifted from the openings, but returns resiliently to cover the openings when the pressure has been relieved. To retain the diaphragm within the valve chamber during the process, some existing designs use various methods of pinning or clamping some portion of the diaphragm to the valve chamber walls, seat or ceiling, or a post running from the valve chamber seat or ceiling through the diaphragm itself, while other designs have retaining posts mounted on the side walls of the chamber to retain a floating diaphragm. Diaphragms which are clamped peripherally to the chamber seat are usually constructed with openings or perforations, or are made of a permeable material to allow the gases to pass through the diaphragm itself. The valve chamber and diaphragm are generally coated with a viscous liquid to aid in the seal.
Existing designs for pressure relief valves of this type perform to a certain standard, but at times still allow gases to bloat the flexible containers to unsightly or dangerous proportions, or still allow reverse flow of air or moisture back into the container. A simple and economically viable pressure relief valve with a performance edge over conventional valves is needed.